Pain is a well known phenomenon as an indicator of actual or potential injury or tissue damage due to inflammation, ischemia, mechanical or other irritation. Treatment of pain includes the use of local anesthetics, which block neuronal transmission and affect sensation as well as pain, and analgesics, which relieve pain and additionally may interfere with the activity of chemical mediators of inflammation.
Loss or damage of epithelial tissue is usually associated with moderate to severe pain and can result from a number of causes, for example, burns, corneal abrasions, other abnormalities of mucosal tissues, and surgical procedures involving epithelial and other tissues.
An example of pain associated with a surgical procedure is surgical correction of myopia by excimer laser photorefractive keratectomy. Following photorefractive keratectomy (PRK), patients generally experience moderate to severe eye pain in the first 24 to 48 hours. Current pain management with bandage contact lens, non-steroidal anti-inflammatory agents, and oral analgesics mitigates, but does not eliminate, the discomfort in most patients (Cherry, Tutton). Topical anesthetics have been used to reduce pain, but due to their short duration of action, frequent administration is required. For example, benoxinate, cocaine, tetracaine, and proparacaine are commonly prescribed topical anesthetics for management of eye pain. These topical anesthetics only provide pain relief for short periods, on the order of 15 to 30 minutes. Given frequently, these agents can be toxic to the corneal epithelium and inhibit re-epithelialization (Rosenwasser).
Thus, there is a need in the art for methods of producing long-lasting, local anesthesia without inhibiting re-epithelialization or healing of other tissues.